Great post Richard! Keep them coming!! May I use it in the gomog Roadster section?
I use NGK as well, abandoning the originally recommended Champions 2-3 decades ago! I use their NGK iridiums as well. Despite their pricer they last MUCH longer than other spark plugs.
An important codicil if I may. plugs are removed and replaced easily with a smear of copper slip on the threads.....they all came out as new with no signs of corrosion, possibly helped by the 30° angle of heads.
In the 1980s, (from memory) some savvy spark plug manufacturers began coating their plug threads with ever more sophisticated solutions to prevent rust, seizing..etc
By the 1990s all manufacturers were doing so. Adding anything became unnecessary, even prejudicial as it can can combine with the manufacturers precaution and definitely changes the important torque readings, by 20%+. It also increases the possibility of the plugs seizing. This is why your old spark plugs came out unseized and pristine.
The use of any other coating is strongly advised against.
https://ngksparkplugs.com/en/resources/5-things-you-should-know-about-spark-plugs More by NGK than even other manufacturers.
But old bad habits die hard. The debate, rather lopsided now, continues. Google "should I use copperslip on spark plugs"
If you choose to remedy, change the plugs and carefully clean the threads in the head.
Be well.
gmg.
